1. THE BEGINNING

The 200-inch Palomar reflector, shown in the famous drawing by Russell
W. Porter in Figure 1, was commissioned for
regular scheduled
observations on November 12, 1949, fifty years to the month of the
distribution of this volume of Annual Reviews. The Hale telescope,
planned since 1929, had enormous publicity surrounding both its
construction and the hopes for astronomy as to what it might
accomplish. The purpose of this review is to discuss the extent to which
those hopes have been realized. Palomar, together with Mount Wilson in
the joint operation known at first as the Mount Wilson and Palomar
Observatories, often lead the way in the explosive developments that
have characterized astronomy in the period.

Figure 1. Drawing by Russell W. Porter of
the 200-inch telescope and its dome made in 1936. Note the roller
bearings at the north pier, replaced in the real telescope by the
oil-pad flotation invention. Note also that the girders of the dome
structure are not covered here as they are in the dome. The dome was
finally completed with a double sheathing for thermal control.

The formal dedication of the Palomar Observatory and of the Hale
telescope took place on June 3, 1948, led by Vannevar Bush, president of
the Carnegie Institution of Washington, and Lee Du Bridge, president of
the California Institute of Technology.

A scientific dedication took place a month later during the joint
meeting of the Astronomical Society of the Pacific and the American
Astronomical Society
(Richardson 1948).
The principal scientific address was by
Walter Baade (1948)
titled "A Program of Extragalactic Research for the 200-inch Telescope."
This was a prescient document, outlining a research program that was to
take 30 years. Much of Baade's lecture will be discussed later.

The telescope was not released to the astronomers for another 16
months. Ira Bowen (Figure 2), hero of that
period and for the following two decades, keeping his head when all
others were losing theirs, knew that if he released the telescope to the
astronomers, even for a few months, he would never get it back. As
director and as one of the world's foremost experts on optics, he was
responsible for bringing the telescope to as high a state of perfection
as the design of the engineers permitted.

Figure 2. The leading players in the early
days of stellar evolution and cosmology at Palomar. Left to right,
top to bottom: Ira S. Bowen, Walter Baade, Edwin Hubble, Milton
Humason, Rudolph Minkowski.

By 1948, two problems had surfaced
(Bowen 1948,
1949).
(1) The lever system that grabbed the honeycomb ribbings at the
back of the five-meter mirror had too much friction by a factor of 30 to
keep the mirror at its proper figure for all gravity
loadings. (2) As it left the optical shop, the mirror had a
slight turned-up edge, purposely, so that its sag in the cell beyond the
radius of the back squeeze levers was expected to compensate for the
raised outer 20 inches. But the mirror did not compensate as was
predicted. It was too stiff.

Thus, Bowen made the very difficult decision to take the mirror out of
the telescope and polish down the turned-up edge on the dome floor. The
final figuring of the outer raised 20 inches was done by Don Hendricks,
the chief optician of the Mount Wilson observatory who had a magical
touch, together with Mel Johnson, one of the opticians who had
originally worked on the mirror from 1936 to 1946 in the Caltech optical
shop (with four years out for World War II).

A long series of optical tests were made after this fix and were
analyzed by Bowen from measurements on the Hartmann test plates. They
revealed that the mirror was nearly perfect. The matter-of-fact
description of these trying tests and his initial decision to remove the
mirror for the fix is described by
Bowen (1950)
in a classic paper entitled "Final Adjustments of the 200-inch
Telescope." He had waited to publish this account until
Hubble (1949)
had written an account called "First Photographs With the 200-Inch Hale
Telescope" in which Bowen is not mentioned, yet the needed mirror
correction is discussed as if the photographs had first revealed the
problem. However, the first photographs had in fact been taken by Bowen
with the telescope, months before, as part of the testing regime. As
great an astronomer as Hubble was, he could never overcome his
disappointment that he had not been chosen as the director of Palomar.

Nevertheless, Hubble's fame, importance, and close association with the
200-inch project through cosmology, which in some sense justified its
construction following his seminal discoveries at Mount Wilson from 1922
to 1936, were the reasons he was given the opportunity to use the
telescope in four observing runs between January 1949 and April 1949,
interspersed with Bowen's Hartmann-testing regime.

The first scheduled run in which the telescope was officially assigned
to an astronomer was on November 12, 1949. That observer was not
Hubble. He had suffered a heart attack in June 1949 before the
completion of Bowen's extensive work.

As important as the 200-inch reflector has been for astrophysics and
cosmology, the Palomar wide field 48-inch Schmidt survey telescope was
in some ways as important in the early years for mapping the northern
hemisphere sky. That era is so long ago that it is difficult to remember
the state of our ignorance of the deep sky before the Palomar Schmidt
Survey. As it turned out, without that mapping, the 200-inch would have
been vision impaired.

The primary 72-inch mirror for the big Schmidt had been completed by
1941 in the Mount Wilson optical shop. The difficult 48-inch correcting
plate, ground and polished to its non-spherical figure by Hendricks, was
completed in the summer of 1948 and the telescope went into routine
operation in January 1949
(Bowen 1948).
Walter Baade had been instrumental in bringing the principle of the
Schmidt optical train back from Hamburg in the early 1930s, having been
a colleague of Bernhard Schmidt, a taciturn Estonian, in the late 1920s
when Baade was still on the staff of the Hamburg Observatory. They had
been members of the Hamburg eclipse expeditions to Lapland in 1927 and
the Philippines in 1929, and were close friends.

The first official Schmidt plate (recorded in the record book on
September 29, 1948) was taken by Hendricks, who was in charge of the
completion of the optics and collimations of the telescope. The
14-by-14-inch plate was of M31, seen for the first time on a single
plate with superior definition and faint limiting magnitude in its full
4° extent. A reproduction of the Hendricks' plate is in Panel 18 of
the Hubble Atlas (Carnegie Publication No. 618). The first published
photographs from the 48-inch Schmidt were by
Minkowski (1949)
who showed them in his description and analysis of the nebula
surrounding the young galactic cluster NGC 2244.

Four wondrous books on Hale and the making of the Hale telescope, of
Palomar itself, and of its predecessor observatories of Yerkes and Mount
Wilson are The Glass Giant of Palomar
(Woodbury 1940),
Explorer of the Universe: A Biography of George Ellery Hale
(Wright 1966, 1994),
Palomar: The World's Largest Telescope
(Wright 1952),
and The Perfect Machine
(Florence 1994).